This section provides a general summary of background information and the comments and examples provided in this section are not necessarily prior art to the present disclosure.
Concrete is a commonly-used construction material. Concrete is very strong in compression, but relatively weak in tension. Reinforcing steel, also known as “rebar,” is a steel bar or mesh of steel wires used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and hold the concrete in tension. Rebar is conventionally fabricated into round shapes for use in reinforced concrete and masonry.
Rebar must meet industry standards, such as ASTM International. A615/A615M-15 Standard for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement, and ASTM International A706/A706M-15 Standard Specification for Deformed and Plain Low-Alloy Steel Bars for Concrete Reinforcement (hereinafter “ASTM A706”), the contents of which are incorporated herein. Rebar used in construction as welded wire fabric or deformed bar anchor studs can alternatively meet ASTM A1064/A1064M-13 (hereinafter “ASTM A1064”). Rebar used in structures subject to certain potential seismic loading, a function of the anticipated intensity of ground shaking and other earthquake effects the structure is likely to experience and the structure's use, must meet the Structural Concrete Building Code, ACI 318-14 (hereinafter “ACT 318”), of the American Concrete Institute, the contents of which are incorporated herein in their entirety.
Rebar can be arc welded. Arc welding, however, is a relatively time-consuming process. Furthermore, if a metal having high carbon content such as rebar is cooled too quickly after arc welding, it gets extremely brittle and hard. Accordingly, arc welding of rebar often involves preheating the material as well as specialized welding equipment and accessories in order to slow cooling and reduce brittleness.
Another technique for fastening rebar to a base metal without the need for welding is to thread an end of the rebar. One such example is illustrated in FIG. 1 (not drawn to scale), in which a threadable rebar 10 includes a steel bar 12 which extends from a first end 14 to a second threaded end 16. A threaded aperture (not expressly shown) is correspondingly created in the base metal and the threaded end 16 of the rebar 10 is then threaded therein to fasten the threaded end 16 of the rebar 10 to the base metal. However, this technique requires specialized equipment and extra steps to manufacture both the threaded end 16 of the rebar 10 and the threaded aperture of the base metal as well as to assemble the threaded end 16 of the rebar 10 into the threaded aperture of the base metal.
Stud welding is a technique for welding a fastener such as a pin, stud or other fastener, to a base metal. The studs are welded to the base metal by establishing an electrical arc between the stud and the base metal to heat the metal at the tip of the stud and the base metal to a molten or liquid state and then plunging the stud into the base metal before the molten metal cools to solid state. Stud welding can be accomplished much more quickly than standard arc welding methods. However, stud welding must meet industry standards as well, such as American Welding Society Structural Welding Code Steel, AWS D1.1/D1.1M:2015 (23rd ed. Jul. 28, 2015) (hereinafter “AWS D1.1”), the contents of which are incorporated herein in their entirety. Additionally, studs must meet the ACI 318 standards if the stud is to be used in structures having certain potential seismic risk.
Rebar can in some instances be stud welded. For example, rebar which meets the dimensional and strength requirements of ASTM A1064 can be stud welded. However, studs made from ASTM A1064 rebar material do not meet the seismic requirements of ACI 318. Accordingly, ASTM A1064 rebar cannot be stud welded in construction applications having a certain level of seismic loading.
Thus, there remains a significant and continuing need for a stud weldable rebar that meet the AWS D1.1 industry standards for concrete construction as well as the ACI 318 standards for construction in seismic risk zones, without the need for pre-heat or specialized welding equipment, processes, or accessories.